Solvent cleaners are known for their cleaning ability, quick drying, metal compatibility, and low surface tension to facilitate penetration. Unfortunately, most of these solvents are known also for the air pollution they cause regarding as volatile organic compounds or VOC), toxicity, flammability, and incompatibility with plastics. Moreover, the use of volatile organic compounds (“VOC”) solvents has been discouraged due to their deleterious effect on the environment. Regulations have been promulgated to accelerate the phase-out of environmentally destructive solvents. The Environmental Protection Agency (“EPA”) promulgates rules and regulations regarding environmental concerns such as VOCs. EPA has defined a VOC to include any volatile compound of carbon which participates in atmospheric photochemical reactivity. Thus, there is a need to reduce the use of conventional VOC solvents. It is apparent that a need exists for a solvent system which has little or no VOC content. The old specification P-D-680 solvent, commonly called Stoddard solvent or mineral spirits, contains petroleum fractions that are complex mixtures of mostly aliphatic hydrocarbons, but may contain some aromatics and olefinics. As such, P-D-680 contains hazardous air pollutants (HAPs) and VOCs, and causes health and environmental concerns. The revision to MIL-PRF-680 eliminated the HAPs but MIL-PRF-680 still covers a petroleum-based solvent containing the same amount of VOCs as P-D-680. These solvents have been specified for general cleaning to remove oil and grease from aircraft and engine components and from ground support equipment.
There are several alternatives to the MIL-PRF-680 solvents: water based, semi-aqueous, and solvent-based cleaners. Water-based cleaners contain detergents to remove grease and oil and may be used hot and/or with various forms of agitation (spray or ultrasonic). Disadvantages include flash rusting, embrittlement of high strength steel and poor cleaning efficiency. Semi-aqueous cleaning processes incorporate not only detergents, but also solvents to improve effectiveness. Some products contain solvents emulsified in water while other contain water-rinsable solvents. A significant disadvantage to semi-aqueous cleaners is their susceptibility to separation. Solvent-based cleaners, however, continue to be used in effective, low cost cleaning processes. In order to retain the capability of solvent cleaning, a new type of solvent is needed to meet the HAP and VOC requirements.
Under the proposed rule, MIL-PRF-680 will no longer be allowed in solvent degreasing operations in the SCAQMD. If a substitute material or process is not authorized, the Aircraft intermediate Maintenance Detachment (AIMD) at Lemoore and other maintenance facilities will not be able to perform specific maintenance requirements in accordance with NAVAIR technical manuals. Since MIL-PRF-680 is the only material authorized by the applicable maintenance manuals to clean flight critical parts, an approved alternative for MIL-PRF-680 was necessary to meet the new environmental regulations.
Specifically, solvent cleaning of aircraft components is performed at organizational, intermediate and depot levels and usually takes place in either spray sinks or batch loaded dip tanks. The primary solvent used for these applications has been P-D-680 Type II, which has a VOC content of more than 750 grams per liter (g/L). P-D-680 (A-A-59601) is a petroleum-based solvent, which contains hazardous air pollutants (HAPs) and volatile organic compounds (VOCs) which causes health and environmental problems. Its successor, MIL-PRF-680 is also a petroleum-based solvent which contains the same amount of VOC as P-D-680 but does not contain HAPs. Alternative processes, to eliminate VOC emission are immersion cleaning with cold or hot water-based products, heated high-pressure spray washing using water-based products, and exempt solvent cleaning. Water-based processes are often ineffective on heavy soils and can result in flash rusting of steel components.
To meet the new environmental regulations, NAVAIR Patuxent River developed a specification MIL-PRF-32295A (Cleaner, Non-Aqueous, Low-VOC, HAP-Free). The new specification consists of three types: Type I is intended for cleaning light soils such as oils and hydraulic fluids, Type II is intended for cleaning heavy soils such as greases and carbon residue, and Type III is intended fbr wipe cleaning applications. Three products have met the qualification requirements of MIL-PRF-32295A Type I specification. Currently, Type I qualified products are listed in NAVAIR 01-IA-509 Manual (Cleaning and Corrosion Control Manual) for cleaning aircraft applications. The cyclicsiloxane compositions of this invention qualify to be used to clean weapon systems across DoD maintenance facilities as an alternative to MIL-PRF-680.